This invention relates to tufting machines and more particularly to tufting machine gauge parts, specifically tufing machine hook mounting arrangements.
It is known in the art to provide tufting machine hooks in modular form, i.e., a plurality of hooks being arranged in sensibly parallel spaced disposition in a common cast body. Modules of this type are illustrated in Bardsley U.S. Pat. No. 4,303,024 dated Dec. 1, 1981, and Slattery U.S. Pat. No. 4,397,249 dated Aug. 9, 1983, both patents being assigned to the assignee of the present invention. Although these hook modules have proved satisfactory in use, it appears that a differential shrinkage between portions of the cast body results in a mutual divergence of the hooks from the body such that parallelism is destroyed. It thus becomes necessary after casting to adjust the hooks, as by bending, to achieve the requisite degree of parallelism therebetween and an acurate pitching out of the hook bills where they must cooperate with mating needles. Although this additional step in forming the module may present some inconvenience, it is readily and easily accomplished with conventional carbon steel and steel alloy hooks since they have the requisite bending qualities.
To improve the wear characteristics of tufting machine hooks which, of course, engage respective needles during each cycle, which may be 1200 times each minute, and in the case of cut pile tufting machines also likewise engage respective knives, materials such as tungsten carbide may be utilized. However, the poor bending qualities of tungsten carbide has to date precluded the use of this material in constructing hooks for use in cast modular bodies. When differential shrinkage occurs, the hooks cannot be bent back into parallelism.